Method of manufacturing battery liners



Patented Nev. '30, 19 26.

uN TEo STATES.

PATENT OFFICE.

ABLIE SCHOBGER, 0 F .MADISON, WISCONSIN, ASSIGNOR, lBY MESNE ASSIGN- HENTS, TO C. F. BURGESS LABORATORIES; INC'., 018' DOVER, DELAWARE, A CORPORA- rronor DELAWARE. v

ammo!) or MANUFACTURING BATTERY Lnmns.

Bo Drawing. Original application flied November 22, 1923, Serial No. 876,288 invited and this application filedOctober 2, 1924. Serial Ko. '741,287.

In the manufacture of dry cells 6" high or higher, and of thetype commonlyused with telephones, or for gas .engineigmtion, or in the filament circuit of radio receiving sets, it is common practice to place a sheet of paper board againstt-he inner surface of the zinc can or electrode to prevent the fine- 1y pulverized mixture of carbonaceous ma ter'ial and manganese dioxide, commonly known as the 1111K fromcoming inconta'ct with the zinc and causing fifSllOlt circuit. The aper board in common use at the pres cnt time for that purposeis somewhat like "blotting paper in appearance and is made up of comparatively loosely adhering fibres. I is highly porous, and in a wet condition has little strength. The pulp used for the manufactureof such paper board has the property 0i fineness, that is, the fibres are Y un elatinized, or at most, are gclatinized or hy rated only to an insignificant amount. Owing to the nature of the pulp from which such'paper boardis made and owing to the manner in which that pulp is formed into sheets, the openings between the fibres of the board are relatively large, with the result that the sheet is highly porous. It has been my experience thatsuch sheets though easily penetrated by the battery electrolyte are porous in an irregular way with .the result that electrical action at the zinc surface is inclined to be localized, and that diifusion of the electrolytic salts through the board does not occur iii-the smooth and even manner essential to most etlicicnt and reliable action of the cell. V

The paper boards of the prior art have other shortcomings well known to battery makers, such as the tendency to tear during assembly of the cell; the danger that line particles ol the mix will sift through the paper intocontact with the zinc"; the resist ance offered to the flow of current from one electrode to the other through the cell, and the slowness of the recuperation after a heavy service demand. and resultant dcplc tion of the electrolyte iu'thc pores of the sheet. v

it have found that if wood pulp, such as unbleached spruce sulphite pnlpyis beaten or ground with water a ,in dry high degree hydration commonly known "as .wetness by paper makers, or until the Such 'a wet gelatinized' board approizi mates parchment paper in the uniformity of'its conductivity for electricity, and inthe uniformity with which it permits diffusion of salts. It is much more plastic than ordinary battery board, and, consequently, when the rnix is. rammed or forcibly tamped into the zinc cup, in accordance with standard practice, there is a more continuous and intimate contact between the board and the zinc surface. In this way the electrical conduct-ivit of thedry cell is increased and rendere more uniform. The battery...boarcl of m'yinvention is much tougher in the wet condition than ordinary board, thus greatly decreasing the liability of rupture during" tamping.

The degree of hydration or gclatinization to which the fibers should be subjected will depend upon ,the kind of pulp employed, and upon the apparatusused for producing gelatinization. I have satisfactorily em ployed ordinary paper makers heaters,

though other apparatus capable of produc -m a grinding or beating action on the pup in water may be used, such,- for instance, as a-ball mill, or a paper makero refiner.

Whatever form cl apparatus is used for mechanically disintegrating the cellulose in water, it should be such as not to reduce the fibers to powder, by a cutting action, but on the contrary, shouldbe such as will bring about the desired cutout of pgelatinization, While preferably leaving some ot the initial fibers present to ".lo'rin a mechanical structure within'theiutcrstices oil while-lithe oi oi disintegrated lihcrc may let held. he

time rccinlred'ior producing ca degree lllil of gelatinization with a paper mixkers beator depends upon the size of the beater, the

speed of the roll, the bluntness of the knive and the extent to which the rollis lowere upon the bed-plate. I have, therefore, deemed it expedient to here set forth in some detail all ofthe operating-conditions essential or importantto the production of resent battery board.

'1- e phenomenon of gelatinization or hydration of cellulose is not. sufiiciently' well understood at the present time to be rigidly tice of the present invention that the exact nature of the changes. should be fully known. It can easil be demonstrated that when chemical woo pulps (cellulose) are subjected to prolon ed beating in the presence of water the 'brous' structure is partranslucent.

tially or totally destroyed, and the pulp acquires a gelatinous consistency. On drying, this gelatinous cellulose is hard and has a horny appearance, and in thin sheets is During drying, it. shrinks greatly and is inclined to warp. It is highly hygroscopic and on boiling with dilute acids at atmospheric pressure has a greater reducing power towardsFehlings solution than is obtained from the same cellulose not gelatinized.

Where the term cellulose is used herezn,

it is to be interpreted in the broad sense as including fibers consisting either entirel of cellulose, such as cotton, or as inclu ing wood fibers not entirely freed from lignin. Practically pure cellulose has ap roximately the formula (C,,H O,,)n, whie wood or ligno-cellulose, on the contrary, contains approximately 30% of lignin, acompound having a higher carbon content than does cellulose and one which does not yield sugars on hydrolysis, as does cellulose. Lignocellulos'e is but slightly soluble, or soluble with great difiiculty in such ordinary-cellulose solvents as zinc chloride solution, Schweitzers reagent, etc.

Gelatinized cellulose whether made from. cotton or from wood and whether pure or contaminated with lignin possesses to ahigh degree the property of retaining a large amount of water when mechanical means such as centrifuging or pressing are employed for removing the latter. It will commonly retain from 300 to 600 per cent of water, by bone dry weight of cellulose content. Another characteristic is its re sistance to penetrance by fats and oils. The two properties of gelatinized cellulose by which that material can be most easily recog nized b battery makers are theihigh shrinkage an the hardness producedwhen a battery board is passed from the wet to the dry condition. In these respects the battery board of the present invention difl'ers from battery board as. commonly made in a man-' ner pronounced and evident, though from their very nature they areibut rough and ready tests of a rather complex di erence. Under circumstances where'the characteristics of shrinkage and hardness have been obscured, as through contact with battery electrolyte or because of age and progressive chemical change, other criteria may be relied on.

Although the \process of manufacturing my improved battery boardmay vary in many details, a method used by ine with success is' as follows: Wood or ligno-cellulose is barked, chipped and then is cooked to a pulp in usual manner as by the. well known sul hite process. This cooking removes 'the lignin and other natural incrusting materials and leaves the woody fibers loosely bound to one another The fibers can then' be separated in usua-l paper-making equipment and ultimately formed into a pulp, although I ampulp, which on passage through a wet as suitable as the above because more time p and power are required to obtain the proper degree of gelatinization. The follow ng data is giyen by way of illustration. A

twenty pound beater, the roll of which has a peripheral speed of 2000 feet per second,

is charged with sulphite spruce pulp and water, and the roll set down'hard upon the bed-plate. Under these conditions with Ito dull knives, a satisfactorily gelatinized pulp isobt-ained by beating for:one hour. -The fibers still retain their structure in-lar epart but are intimately .mixed and coats with gelatinized cellulose. The pulpy mass is next passed-to a pa er machine or board machine, and there is shaped into a sheetor board of the required thickness. The material is still very wet when it comes from the press roll of the gzper machine, and in that condition may regarded as consisting: essentially of a skeleton of loosely v interlaced cellulose fibers, the interstices between the fibers being filled in with the gel that has resulted from complete or artial gelatinization' of some of the cello ose fibers. The material is not porous in the sense that there are holes or openings tending in irregular mannec through it, but t IS porous the Sense that electrolytic salts readily penetrate into and through t e gel, and so can be transferred rea-dlly from one side to the other of the battery board. The board is preferably used in the wet condition in which it comesv from the press roll of-the paper machine. As an example, a. battery board 6 by 8" and 0.065 inch thick when ready for use will weigh about 60 grams. That same board if thoroughly dried would weigh about 20 ams, and would be very hard and have a eather-like appearance. Shrinka e of the board'from the wet to thedry con ition per foot varies from of an inch when the measurement is made on the board in the direction inwhich the sheet travels'on the paper machine to about 1 across the sheet.

I do not intend to limit myself to the above degree of gelatinization, nor to the dimensions set forth above, and have given said information only by way of illustration.

A battery liner produced as above described is very tough and stron while wet,

' being in this respect marked y different from ordinary battery boards Ithas no pores or interstices through which fine particles of the mix can filter into contact with the zinc. When the mix is being tamped into the zinc-cup which serves the double function of electrode and container, there is less danger of tearing the paper lining, and

what is perhaps more important, there is less danger of air pockets o'r imperfect contact between the paper lining and the zinc surface. The electrolytic salts readily diffuse from the mix into the paper partition,

and that diffusion is much more prompt, and much more uniform than with battery boards made in usual manner. All of these features contribute to an increase in the flash or short circuit amperage of the dry cell and that increase'according to my experience is to 40% over the flash of standard size cells as ordinarily constructed.

The recuperation of the cell after heavy demands' on it is more prompt because of the greater speed and the greater uniformity with which the electrolyte travels througi the elatinous carrier. The uniformity of the oard tends towards even distribution of electrolytic action on the zinc with less likelihood of pitting and there is more etdirected particularly to the ficient life for the cell over a period of months, whether on intermittent service or merel standing idle on the shelf of a dealer.

Although the above description has been reduction of these improved battery liners rom a cooked wood pulp, such as a spruce sulphite pulp. I am aware that other cellulos1c material can be used, for I have found that the raw material may consist of either cellulose as such or combined with lignin and other natural incrusting materials. In the latter case, if most of the original incrusting materials are present, the beating or other operation for effecting mechanical disintegration and chemical chan e to gelatinized cellulose must be of a more drastic character because of the greater difficulty of producing therefrom the gel needed for filling the interstices between the ungelatinized or partially gelatinized fibers. However, chemical wood pulps retaining a portion of the incrustants, gelatinize more readily than wood pulps completely freed from the same.

. As a modification of the preferred process above outlined, and instead of stoppin gelatinization while some of the fibers still retain their fibrous form, the gelatinization by. more prolonged beating may be carried on until substantially all of the fibers have been converted itno a structureless gelatinous mass. Such a mass does not have enough stren h for use as a battery liner, but that deficiency can be'supplied by add-,- ing to it fibers that have not passed through the disintegrating treatment in the beater. For example, I have found that a satisfactory battery liner can be made by gelatiniz- 'ing a portion of the sulphite pulp to the point where it approaches a structureless mass, then adding some of the original fibrous pul to give the board strength in the wet con ition, then intimately mixing the whole, and ultimately shaping it into boards or liners. lVhen the latter method of manufacture is employed, the fibers added to the structureless mass need not be of the same quality nor even of the same origin as the fibers su plied to the beater for gelatiniza- I tion. T ey may have been produced bygrinding wood, and, therefore, containing much lignin and other incrusting materials. They can even be of mineral or animal origin, such as asbestos wool, or hair, or

mixtures of these with one another, or with 1'. The method of making a battery liner which consists 'in forming. a pulp of fibers interspersed with gelatiniaed cellulose and- .water, forming said pulp Into a sheet, and.

shapingsaid sheet into a liner while still wet, substantially a described. I

2. The method of making a battery liner which consists in forming a pulp of cellulose fibers interspersed and coated with elatinized cellulose and water, forming sai pulp into a sheet and shaping said sheet into a liner while still wet, substantially as described. v a

3. The method of making a battery liner which consists in beating cellulose fibers in water to produce gelatinized cellulose, forming a wet sheet from said gelatinized cellulose interspersed with fibers, and shaping said sheet while still wet into a liner.

4. The method of making a battery liner which consists in beating wood pulp in water until much of the pulp has been changed to a structureless mass,then forming a wet sheet from said structureless mass and from fibers, and then shaping said sheet while still wet into a liner.

t 5. The method of making a battery liner which consists in beating chemical spruce pulp until there has been produced therefrom a relatively large quantity of gelatinized cellulose, mixing ungelatinized fibers with the material so produced, and shaping ture.

ARLIE WILLIAM SGHORGER.

aflix my signa- 

